Catch 22

Chromosome 22 is one of the smallest of our 23 pairs of chromosomes. But we still don't know whether it is gene-rich. So far, the chromosome has been linked with schizophrenia, chronic myeloid leukaemia and trisomy 22, the second most common cause of miscarriages. At least 27 diseases involve some genetic component of the chromosome, which is frequently implicated in tumor progression. However, half its genes are yet to be characterised. Their sheer variety, in terms of differing lengths, is of considerable interest ( Nature , Vol 402, No 6761).